Maintenance
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Forward braking
In the free position, with the handbrake
fully forward in the OFF position, the
drawshaft of the overrun device is fully
extended and the shoes are clear of the
drum.
As the towing vehicle brakes, or starts
to drive downhill, the drawshaft of the
overrun device is depressed toward the
unit being towed. This action imparts
linear motion to the main shaft of the
overrun device which transmitted via the
overrun lever, brake rod and Bowden cable
to the expanding clutch. This mechanism
forces the leading brake shoe and by
reaction, the trailing shoe outwards into
contact with the drum.
Friction between the brake shoes and the
drum creates a tendency for both shoes
and the expanding clutch to move in the
direction of forward rotation until they abut
the adjuster box. This ensures that both
shoes remain in the braking position.
Reversing
When the towing vehicle reverses, the
drawshaft is pushed backward, moving the
overrunning device through its full travel.
This movement is transmitted in the
normal manner to the expanding clutch.
The clutch forces both shoes into contact
with the drum. Initial friction between
these creates a tendency for the shoes
and the expanding clutch to move in the
direction of the wheel rotation i.e. reverse.
This movement imparts pressure to the
spring-loaded auto-reverse lever, causing
it to collapse. Thus, friction between the
shoes and drum is almost eliminated,
allowing the trailer to reverse in concert
with the towing unit.
Slight forward movement of the chassis
will allow the coiled spring to reassert
itself, enabling the reverse lever to recover
to its normal position. Normal braking is
then immediately available.
Parking
The AL-KO parking brake system
incorporates a patented device for added
safety when parking on a reverse-sloping
site or steep hill.
The AL-KO parking brake system
comprises a handbrake lever mechanism
actuating a Bowden cable, which operates
a brake unit assembly, contained within
the wheel hub.
AL-KO’s unique parking brake system
requires a source of stored energy to lock
the wheel brakes should the trailer start to
move after it has been uncoupled from the
towing unit.
This energy source is provided by a spring
cylinder acting as an energy store.
Wheels and tyres
Wheels
The AL-KO chassis is supported on road
wheels fitted with pneumatic tyres. The
size of wheel and type fitted to the chassis
is dependent upon the load to be towed.